Recently, many attempts are carried out to obtain a higher fabric quality by improving feeling of cloths through modification of the fiber section from a circle to, e.g. a star or combination of two or more polymers.
However, an improvement in deep color of fibers causes a reduction in luster thereof due to occurrence of dullnes and degradation of brightness. On the other hand, an improvement in luster causes a reduction in deep color due to increased surface reflection. The two are very difficultly compatible with each other.
JP 43-14185 discloses iridescent coated-type composite fibers including three layers. The fibers produce slight coloring by reflection and interference of light, but cannot show a deep interference color having a reflection spectrum with a predetermined wavelength due to insufficient number of layers.
Some references such as JP-A 59-228042, JP-B2 60-24847, and JP-B2 63-64535 propose coloring fibers or textiles including flat filaments obtained by joining different polymers. However, lamination of such flat filaments enables difficultly the thickness which allows interference of light, merely serving, theoretically, to restrain reflection light. The references define the shape of the flat section of a fiber for producing a color, and an angle of the longitudinal axis thereof with respect to the surface of a textile in any portion except a so-called structure point where warp and wheft cross completely so as to reinforce a coloring function of the textile. The references fail to show, however, various conditions indispensable to coloring by interference of light, such as thickkness and length of a layer and refractive index of a component, lacking practicability.
A journal of the Textile Machinery Society of Japan Vol. 42, No. 2, pp. 55-62, 1989 and Vol. 42, No. 10, pp. 60-68, 1989 describes laminated photocontrollable polymer films for producing colors by interference of light, wherein a film with anisotropic molecular orientation is interposed between two polarizing films. However, the films cannot be transformed into fine fibers or minute chips, having limited scope of application. Moreover, though the films produce an iridescence, a desired color cannot be obtained due to difficult control of a dominant wavelength to be reflected.
One method of producing a color by reflection and interference of light is to closely fill a fiber with particulates with uniform diameter such as latex particulates. However, fixing of the latex particulates is difficult to be done upon manufacturing to lose often a regularlity of arrangement thereof, obtaining no coloring function. Thus, this method is possible theoretically, but not pracitically.
It is, therefore, an object of the present invention to provide fibers with optical function which ensure, with improved feeling, production of a desired color or interception of infrared or ultraviolet rays by reflection and interference of radiation.